let add = (a,b)=>a + b;
let sub = (a,b)=>a - b;
let mul = (a,b)=>a * b;
let div = (a,b)=> (b != 0) ? a / b :'除数不能为零';

module.exports = {
    mul, div
}
module.exports.add = add;
module.exports.sub = sub;
